1. Field of the Invention
The present invention relates to a technique for implementation of a Peltier controlled sample in a polarimeter.
2. Brief Description of Related Art
As a person skilled in the art would appreciate, a polarimeter is an instrument known in the art for measuring optical activity exhibited by an optically active substance. In operation, the plane of polarization of a linearly polarized light beam may be rotated when passing through the optically active substance, and the rotation may be determined by the specific substance, the concentration of that substance and the optical path length of the light through the substance contained in the sample cell, whereby the concentration of the specific substance can be calculated by the measured rotation. The optical rotation may also be affected by the temperature of the substance contained in the sample cell, and thus it may be desirable, and in many cases required by governing regulations, that the temperature of the sample substance be controlled to be at a set point for precise measurement.
With this backdrop, and by way of example, some known techniques for implementation of a Peltier controlled sample using such a polarimeter may include the following technique:
Known techniques for implementation of a Peltier controlled sample in a polarimeter may include using a sample cell that is a cylindrical tube so as to minimize the amount of the sample substance that is in the cell but not in the light path, referred to as “dead volume”. Flanges are provided at opposite ends of the sample cell, each with a beam aperture therein for allowing the polarized light beam to pass therethrough. The flanges are usually standard in size for properly positioning the sample cell in the light path when the pair of flanges sit on the cell holder constituted by a parallel rails. The flanges may be removable from the sample cell to facilitate cleaning of the sample cell. The temperature control of the sample substance is realized by circulating water in a water jacket around the external surface of the sample cell containing the sample substance. The water jacket is formed by an outer tube communicated with a water tube connected to a water source at a predetermined temperature. However, as a person skilled in the art may appreciate such a water temperature control system is complicated in structure, comprising a water jacket and cooling tubes. Furthermore, as a person skilled in the art may also appreciate it is inconvenient to connect and disconnect the tubing when cleaning the cell and changing the sample, and it also takes long time to change the temperature set point.
Other known techniques for implementation of a Peltier controlled sample in a polarimeter may include thermoelectric temperature control techniques, such as thermo electric coolers (TEC). For example, the temperature of one side of a TEC device, which is usually a flat plate in shape, is controllable by an electric current. Heat can be made to flow through the device in either direction as required. A TEC element with a heat sink is provided to be thermally conductive with a rectangular cell holder accommodating a rectangular sample cell. A polarized light beam passes through the sample cell via the apertures provided on the cell holder. The solid TEC element appears to eliminate the complication and inconvenience of the water tubing required in the conventional cylindrical cell samples. Furthermore, the temperature of the cell holder and therefore the sample cell can be easily and quickly controlled at a set point. However, the rectangular sample cell assumes a high dead volume and requires a larger sample volume to fill. This is costly when the measured substance is precious. Another problem with such a rectangular structural design appears to be that the cell holder cannot work with conventional standard cylindrical sample cells which are commonly used in the industry. In addition this design was not able to control temperature within the limits required by relevant governing regulations.
Still other known techniques for implementation of a Peltier controlled sample in a polarimeter may include using a combination of a slanted flat base plate and a single horizontal rail, e.g., where the slanted flat based plate is made of heat conductive material for transferring heat between a thermal electric conductor (TEC) and a material inside a sample cell, where the flat slanted based plate is biased to urge the sample cell against the single horizontal rail, and the combination positions the sample cell at a predetermined position such that a polarized light beam longitudinally passes through the sample cell.
Still other known techniques for implementation of a Peltier controlled sample in a polarimeter may include using a combination of a slanted flat base plate and a stopper or side wall to position a sample cell at a predetermined position such that a polarized light beam longitudinally passes through the sample cell.
Still other known techniques for implementation of a Peltier controlled sample in a polarimeter may include using a combination of parallel rails and a base plate having a dovetail connection to a base plate that is mounted on top of a sample cell, where the base plate is not secured relative to a light beam path and has no position function into relation to same.
Other techniques for implementation of a Peltier controlled sample using such a polarimeter are also known in the art and not set forth therein, e.g., including those set forth in prior art provided to the Patent Office during the prosecution of this patent application.